The period of the pendulum doesn't determine the length of the string.
It's the other way around.
The period of the pendulum is proportional to the square root of its length.
So if you want to triple the period, you have to make the string nine times
as long as it is now.
Answer:
Magnetic force, 
Explanation:
Given that,
A beryllium-9 ion has a positive charge that is double the charge of a proton, 
Speed of the ion in the magnetic field, 
Its velocity makes an angle of 61° with the direction of the magnetic field at the ion's location.
The magnitude of the field is 0.220 T.
We need to find the magnitude of the magnetic force on the ion. It is given by :

So, the magnitude of magnetic force on the ion is
.
Answer:
The correct answer is 24.
Explanation:
Answer: The Electrostatic force of attraction or repulsion between two charges shows that the Newton's third law applies to electrostatic forces.
Explanation: Consider two Oppositely charged charges separated by distance d.
The electrostatic force exerted by charge 1 on charge 2 is.
By Coulomb's Law :
F1 = k
.....................................(1)
The electrostatic force exerted by charge 2 on charge 1 is.
F2 = - k
................................. (2)
negative sign shows that force are in opposite direction.
From Equation 1 and 2
F1 = - F2
Which implies Newton Third law.